Canvas Gauge shows the wrong Value

hi
i try to setup a thermometer which shows also negative values. but how can i set it up that the shown value is correct. as you can see the are below zero is very small compared with the big range above zero.The value box shows the right value but the needle is already in the negative temperature area.

Bildschirmfoto 2021-10-24 um 11.09.07

        - type: custom:canvas-gauge-card
          entity: sensor.pizzaofen_max31855_probetemperature
          name: Oberhitze
          card_height: 210
          shadow_height: 12%
          font_size: 1em
          gauge:
            type: "radial-gauge"
            width: 220
            height: 220
            borderShadowWidth: 0
            borderOuterWidth: 0
            borderMiddleWidth: 0
            borderInnerWidth: 0
            minValue: -20
            maxValue: 800
            startAngle: 40
            ticksAngle: 280
            units: "°C"
            majorTicks:
              ["-20", "0", "100", "200", "300", "400", "500", "600", "700", "800"]
            minorTicks: 2
            strokeTicks: true
            highlights: [{ "from": 600, "to": 800, "color": "rgba(200, 50, 50, .75)" }]
            borders: false
            animation: false
            title: "Oberhitze"
            valueBox: true![Bildschirmfoto 2021-10-24 um 11.07.14|594x466]